This proposal seeks funds to purchase an LCQ TM MS n ion trap mass spectrometer system (Finnigan Corp., San Jose, CA) for the Biomedical Mass Spectrometry Core Laboratory located in the Department of Pharmacology of New York Medical College, Valhalla, NY. The new instrument will be utilized in the electrospray ionization (ESI/MS) mode and in the electrospray tandem mass spectrometry mode (ESI/MS/MS) to elucidate structures of new complex biomolecules. The new instrument will be used primarily for analyses of arachidonic acid (AA) metabolites which cannot be analyzed using our existing GC/MS instrument (HP 5989A, Mass Engine). These include phospholipids containing esterified hydroxy-AA (HETE), glutathione conjugates of epoxy-AA (EET), diglycerides containing HETE, glucuronide of 20-HETE, and nucleic acid epoxyallylic alcohol adducts. These compounds in an intact form are not suitable for GC/MS analyses primarily because of high polarity and thermal instability. We also plan to develop methods to analyze, quantitatively and simultaneously, several AA metabolites in one injection. This will allow for a more comprehensive look into metabolism of AA by cytochrome P450 and lipoxygenases. In one project, we propose to study the chemistry of the reaction of glutathione with peroxynitrite which requires analysis of nitro- and nitrosoglutathione. We obtained preliminary data which suggest that these compounds are well analyzed by ESI/MS/MS. The proposed analyses focus on the generation of the new compounds in the vascular system, in the kidney, and in tumor cells and the new data is expected to provide significant advances in the areas of vascular biology, renal function and cancer. The major user group consists of six scientists funded by the NIH (3 MERIT awardees and 2 Program Project Grant Investigators) who have projects addressing various areas of pharmacology and biochemistry of vascular system, kidney and cancer. The long term goals are to provide ESI/MS(/MS) analyses for long-term funded projects as well as for new projects. The new instrumentation will lead to major advances in understanding the role of eicosanoids, and glutathione in health and disease.